Preparation Of Graphene Oxide/Organic Hybrid Silica Composites And Their Adsorption Properties

Graphene oxide is a research hotspot in the field of material chemistry,due to its excellent thermal and chemical stability,large specific surface area and presence of large amount of oxygen-containing functional groups.Organic hybrid silica not only has the characteristics of inorganic silica,such as low density,low toxicity,excellent biocompatibility,but also contains organic functional groups which expand its application.The composites containing graphene oxide and organic hybrid silica have greater values in practical applications,so their fabrication and applications have become one of the hotspots in the field of material chemistry.In this work,two methods are utilized to fabricate graphene oxide/organic hybrid silica composites with different morphologies.Here are the main contents of the research:1.The preparation of graphene oxide/organic hybrid silica composites with ex-situ method.Firstly,graphene oxide was prepared via Hummer method.Secondly,mercaptopropyltrimethoxysilane（MPTMS）,thiocyanopropyltriethoxysilane（TCPTES）,cyanopropyltriethoxysilane（CTES）and vinyltriethoxysilane（VTES）were separately served as the precursors to prepare organic hybrid silica by one-step method,and the organic hybrid silica was dispersed into ethanol containing acid.Finally,the graphene oxide/organic hybrid silica composites were prepared by mixing the two suspensions.The composites were characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,infrared spectroscopy（FTIR）,X-ray photoelectron spectroscopy（XPS）and X-ray diffraction（XRD）.The experimental results showed that the acid treatment of organic hybrid silica was the crucial procedure to prepare graphene oxide/organic hybrid silica composites.Graphene oxide and organic hybrid silica were composited via electrostatic attraction,and new chemical bonds were not formed between them.Organic hybrid silica was wrapped by graphene oxide in the ex-situ method.When the temperature was 70℃,the quality of graphene oxide and organic hybrid silica was 60 mg and 120 mg,respectively,it was relatively suitable condition for preparing the graphene oxide/organic hybrid silica composites.2.The preparation of graphene oxide/organic hybrid silica composites with in-situ method.Firstly,graphene oxide was prepared via Hummer method.Secondly,the precursors of the organic hybrid silica including MPTMS,TCPTES,CTES,VTES,hydrolyzed and condensed in the suspension of graphene oxide to prepare graphene oxide/organic hybrid silica composites by one-step method.The composites were characterized by SEM,TEM,FTIR,XPS and XRD.The experimental results showed that organic hybrid silica was embedded in graphene oxide sheets in the in-situ method.Similar to the ex-situ method,no chemical bond was formed between graphene oxide and organic hybrid silica.When the temperature was 40℃,the quality of graphene oxide was 40 mg,and the volume of organosilane was 1 mL,it was relatively suitable condition for preparing the graphene oxide/organic hybrid silica composites.3.The adsorption properties of graphene oxide/organic hybrid silica composites.The adsorption properties of the composites were studied by using Cd²⁺as the adsorbate,and the adsorption time,pH,the initial concentration of Cd²⁺and the reusable time of adsorbents as the parameters.The experimental results showed that the adsorption properties of graphene oxide/organic hybrid silica composites were better than that of organic hybrid silica.The adsorption properties of graphene oxide/organic hybrid silica composites prepared by ex-situ method were better than that prepared by in-situ method.Graphene oxide/organic hybrid silica composites had relatively excellent adsorption properties,as the adsorption time was 15 min,pH was6,the initial concentration of Cd²⁺was 140 mg/L.After the composites were used for8 times,their adsorption capacity was 60-65%of the initial adsorption capacity.The isothermal adsorption process was the Langmuir model,the kinetics of the adsorption process was quasi-second-order kinetics model,and the thermodynamics of the adsorption process was endothermic and spontaneous.